FIELD OF THE INVENTION
The invention relates in general to vapor generators and in particular to a new and useful tube spacing grid for the guidance of tubes which is formed of intersecting grid rods and surrounded by an outer ring frame which has an interior encircling groove.
Known are so-called spacers for the pipes of pipe equipment having a nest of pipes (DE-PS No. 22 62 621) where the grid rods of the grid are fastened to an annular frame in such a manner that the frame has on its outer face holes; and has on its inside an encircling groove with rod or bushing receiving lateral slots forming retention means for the grid rods. In this construction the grid, frame and steam generator wall are rigidly interconnected.
In a grid shaped guide retainer for heat exchanger tubes according to DE-PS No. 24 15 242, the rods of the grid have, at the outer rim zone of each grid grate, grooves engaged with radial play by projections of the frame. Grid grates and frames are made of different materials and react differently to temperature changes and the design of this grid is complicated and expensive. The design of the spacers necessitates preassembly of the grid without the frame, and only thereafter can turning for final assembly be performed.